This invention relates to angle encoding apparatus and more particularly to apparatus for encoding a present angular position of a rotating object and to develop an output signal indicative of said position. Many rotating objects are rotated about a cylindrical shaft which supports the object and which is driven by a suitable drive mechanism such as a motor and so on.
There exists a number of devices which are employed for encoding the angular position of the rotating shaft. These devices are referred to as shaft angle encoders. Certain prior art encoders employ a disk upon which a code pattern is impressed. The disk is coupled to a shaft and is concentric with the shaft. As the shaft rotates, the disk rotates and a code pattern is impressed on the disk. The code pattern is indicative of the angle or the position of the shaft about its circumference. Hence, one can read the code by means of electrical or optical transducers and provide an output indicative of the code and therefore, indicative of the current angular position of the rotating object.
There are other types of encoders which operate in various ways in order to determine the angular position of an object when subjected to rotation. Examples of such devices may be had by referring to the following patents:
U.S. Pat. No. 3,767,902 entitled ENGINE MEMBER POSITION PREDICTOR describes a system for predicting the position of a moving member of an automobile engine such as a crank shaft.
U.S. Pat. No. 3,916,186 entitled SPINNING VANE SHAFT POSITION ENCODER describes a system whach reads the positions of one or more coaxial shafts in terms of time intervals produced by optical scanning.
U.S. Pat. No. 3,935,570 entitled SPINNING DISK SHAFT POSTIONING CODER describes a system which reads positions of coaxial shafts as above described by responding to interception invervals of a beam of light.
Still other patents exist which show various techniques for determining angle position of various rotating objects.
Certain disadvantages exist with prior art encoders. Some of these encoders have to be physically connected to the rotating object or the shaft. This, of course, poses many problems in regard to rotating objects where the shaft is not easily accessible as, for example, the drive shaft of a jet engine and so on. More important is the fact that the prior art devices based on construction and so on, impose severe limits on the maximum angular velocity at which they can be used. Thus, there is a problem in using such encoders in high speed rotating equipment.
It would therefore be an object of the present invention to provide apparatus for encoding the angular position of a rotating object employing simple and reliable apparatus while further eliminating the need for making a physical connection to the object or to the shaft associated with the object. The apparatus to be described enables one to encode the angular position of high speed rotating objects; which objects do not necessarily have to be associated with an accessible shaft.